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From: Oliver Upton <oliver.upton@linux.dev>
To: Jinqian Yang <yangjinqian1@huawei.com>
Cc: yuzenghui@huawei.com, maz@kernel.org,
	linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
	linux-kernel@vger.kernel.org, liuyonglong@huawei.com,
	wangzhou1@hisilicon.com
Subject: Re: [PATCH v2 3/3] KVM: arm64: Make ID_AA64MMFR1_EL1.VH writable from userspace
Date: Mon, 8 Sep 2025 22:32:35 -0700	[thread overview]
Message-ID: <aL-788d0xWThAVSl@linux.dev> (raw)
In-Reply-To: <20250909034415.3822478-4-yangjinqian1@huawei.com>

Hi Jinqian,

On Tue, Sep 09, 2025 at 11:44:15AM +0800, Jinqian Yang wrote:
> Allow userspace to downgrade VH in ID_AA64MMFR1_EL1. Userspace can
> only change this value from high to low.

I'm afraid we can't allow this. When we expose FEAT_VHE to the VM,
HCR_EL2.E2H is RES1. Meaning, vEL2 is unconditionally in a VHE
context.

I would be OK with a clarifying comment documenting why the field is
non-writable.

Thanks,
Oliver

  reply	other threads:[~2025-09-09  5:32 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-09-09  3:44 [PATCH v2 0/3] KVM: arm64: make EL2 feature fields writable in ID_AA64MMFR1_EL1 Jinqian Yang
2025-09-09  3:44 ` [PATCH v2 1/3] KVM: arm64: Make ID_AA64MMFR1_EL1.HCX writable from userspace Jinqian Yang
2025-09-09  7:07   ` Oliver Upton
2025-09-09 10:10     ` Marc Zyngier
2025-09-09 21:38       ` Oliver Upton
2025-09-10  1:57         ` Jinqian Yang
2025-09-09  3:44 ` [PATCH v2 2/3] KVM: arm64: Make ID_AA64MMFR1_EL1.TWED " Jinqian Yang
2025-09-09  3:44 ` [PATCH v2 3/3] KVM: arm64: Make ID_AA64MMFR1_EL1.VH " Jinqian Yang
2025-09-09  5:32   ` Oliver Upton [this message]
2025-09-10  1:42     ` Jinqian Yang
2025-09-09  7:00 ` [PATCH v2 0/3] KVM: arm64: make EL2 feature fields writable in ID_AA64MMFR1_EL1 Oliver Upton
2025-09-10  1:42   ` Jinqian Yang

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